Divers, meanwhile, pulled out a woman's body from the capsized Costa Concordia on Sunday, raising to 13 the number of people dead in the Jan. 13 accident.
Civil protection official Francesca Maffini told reporters the victim was wearing a life vest and was found in the rear of a submerged portion of a ship by a team of fire department divers.
Earlier, Italian authorities raised the possibility that the real number of the missing was unknown because some unregistered passengers might have been aboard. As of Sunday, 19 people are listed as missing, but that number could be higher.
"There could have been X persons who we don't know about who were inside, who were clandestine" passengers aboard the ship, Franco Gabrielli, the national civil protection official in charge of the rescue effort, told reporters at a briefing on the island of Giglio, where the ship, with 4,200 people aboard rammed a reef and sliced open its hull on Jan. 13 before turning over on its side.
Gabrielli said that relatives of a Hungarian woman have told Italian authorities that she had telephoned them from aboard the ship and that they haven't heard from her since the accident. He said it was possible that a woman's body pulled from the wreckage by divers on Saturday might be that of the unregistered passenger.
But one of Concordia's officers, who's recovering from a broken leg suffered during the evacuation, dismissed the allegation that such passengers were on the ship.
"Everyone is registered and photographed. Everything's electronic," the Italian news agency ANSA quoted Manrico Giampedroni as saying.
Authorities are trying to identify five corpses who are badly decomposed after spending a long time in the water.
Gabrielli said they have identified the other eight bodies: four French, an Italian, a Hungarian, a German and a Spanish national.
The missing include French passengers, an elderly American couple, a Peruvian crewwoman and an Indian crewman and an Italian father and his five-year-old daughter. Some of their relatives were briefed by rescuers Sunday, and also met with Pierluigi Foschi, the CEO of Costa Crociere, SpA -- the ship's operator -- who viewed the crippled cruise liner from a boat.
France's ambassador to Italy, Alain Le Roy, recounted Foschi's visit.
"He came to see the families, all families. He met the French family. He met the American family. I am sure he is meeting other families, mostly to express his compassion ... to say that Costa will do everything possible to find the people, to compensate families in any way."
The search had been halted for several hours early Sunday, after instrument readings indicated that the Concordia has shifted a bit on its precarious perch on a seabed just outside Giglio's port. A few meters (yards) away, the sea bottom drops off suddenly, by some 20-30 meters (65-100 feet), and if the Concordia should abruptly roll off its ledge, rescuers could be trapped inside.
When instrument data indicated the vessel had stabilized again, rescuers went back in, but only explored the above-water section and evacuation staging areas where survivors have indicated that people who did not make it into lifeboats during the chaotic evacuation could have remained.
Passengers were dining at a gala supper when the Concordia sailed close to Giglio and struck the reef, which is indicated on maritime and even tourist maps.
There are also fears that the Concordia's double-bottom fuel tanks could rupture in case of sudden shifting, spilling 2,200 metric tons (almost 500,000 million gallons) of heavy fuel into pristine sea around Giglio, which is part of a seven-island archipelago in some of the Mediterranean's most pristine waters and a prized fishing area.
But Gabrielli said pollutants found near the ship have been detergents and other substances, including chlorine, apparently from the wreck of the ship, which carried some 3,200 passengers and a crew of 1,000. Any fuel traces found were "compatible with what you find in a port," he said.
Ferries and cargo ships regularly call at Giglio's port.
Sophisticated oil-removal equipment has been standing by, waiting for the search-and-rescue operations to conclude before workers can start extracting the fuel in the tanks.
Giglio Mayor Sergio Orpelli told Sky TG24 TV that it was tentatively planned to begin fuel-removal operations on Monday but that the timetable ultimately depends on when the rescue efforts are concluded. "No hopes have been abandoned that someone might still be alive," Orpelli said.
Coast guard and fire rescue teams have said that the search will go on, as long as the weather holds and the Concordia stays stable.
The Italian captain, Francesco Schettino, is under house arrest as prosecutors investigate him for suspected manslaughter, causing a shipwreck and abandoning the ship while many were still aboard.
Operator Costa Crociere, a subsidiary of U.S.-based Carnival Cruise Lines, has said that Capt. Schettino had deviated without permission from the vessel's route in an apparent maneuver to sail close to the island and impress passengers.
Schettino, despite audiotapes of his defying Coast Guard orders to scramble back aboard, has denied he abandoned ship while hundreds of passengers were desperately trying to get off the capsizing vessel. He has said he coordinated the rescue from aboard a lifeboat and then from the shore.
Rome daily La Repubblica, citing what Schettino allegedly told prosecutors in Grosetto, Tuscany, when he was interrogated last week, quoted him as saying that Costa Crociere was aware of the "recurring practice" of nearing coastlines to salute those ashore. Schettino is quoted as saying that such a maneuver was planned by Costa executives before the ship left the port of Civitavecchia before dinner time on Jan. 13 to gain publicity for the company.
It was not immediately possible to confirm Schettino's allegations. Prosecutors cannot comment on details of a probe while it is still being conducted, and the office of Schettino's lawyer was closed Sunday.
Marco De Luca, a Costa Crociere lawyer, said the company is "an injured party" in the tragedy, which Costa executives have blamed on the captain's failure to follow the programmed route.
Giglio Mayor Orpelli said such "salutes" by passing cruise ships are rare.
Orpelli insisted that before the ill-fated Jan. 13 approach by the Concordia near the reef, the last previous time was on Aug. 14, when the island was celebrating a summer festival in the port, and that the maneuver was closely coordinated with island and navigational authorities. That summer salute was "carried out in perfect safety," the mayor told Sky, adding that he thanked the captain of that voyage "and told him to thank his crew."
Orpelli said that island officials were unaware of the Jan. 13 plan for such a salute.